The present invention relates to an accurate method and apparatus for controlling the flow rate of intake air of an engine.
There are two general types of methods for controlling fuel injection type engines. One is the air-first control system in which air taken into the cylinders of an engine (hereinafter referred to as xe2x80x9cengine intake air flow rate. The result of measurement by an air flow meter provided in a intake pipe is simply referred to as xe2x80x9cair flow ratexe2x80x9d) is measured and then the fuel is injected in an amount in accordance with the engine intake air flow rate. The other is the fuel-first control system in which an amount of fuel is defined in advance and an engine intake air flow rate in accordance with the same is supplied to the engine.
In either of the systems, it is important to achieve an air fuel ratio that realizes a state of combustion desirable for reduction of harmful components in exhaust gas and reduction of the amount of fuel consumption.
Referring to the air-first control system, methods for controlling an internal combustion engine aimed at maintaining an air fuel ratio accurately during a transient time are disclosed in, for example, Japanese patent Application Laid-Open 104930/1990 (hereinafter xe2x80x9cfirst prior artxe2x80x9d) and Japanese patent Application Laid-Open 134136/1992 (hereinafter xe2x80x9csecond prior artxe2x80x9d).
In the first prior art, a technique is disclosed in which an amount of fuel injection is determined by calculating a flow rate of intake air to an engine in accordance with a model of a intake pipe. In this case, a delay in an engine intake air flow rate at the time of a movement of a throttle valve caused by an accelerator pedal is calculated using pressure and engine speed information, and the amount of fuel injection is corrected in association with the delay of air. Since this method has had a problem in that amount for fuel correction is slow because the correction is calculated after a change in the opening of the throttle valve occurs, the second prior art provides a fuel injection controller by introducing a delay to the opening of the throttle valve relative to an acceleration pedal stepping-on amount to reduce the effect of the correction delay.
However, both of the conventional techniques are intended for the air-first control system and have the following problems when used for engines utilizing the fuel-first type control, e.g., direct injection in cylinder engines (hereinafter referred to xe2x80x9cDI enginesxe2x80x9d which imply both of spark ignition type and compression ignition type DI engines). In a DI engine, as its name implies, fuel is directly injected into the combustion chamber of the engine. It is therefore an engine convenient for fuel-first type control because an amount of fuel to be used for one cycle of combustion can be supplied each time. However, since the conventional technique is intended for the air-first type control system, there is a need for an apparatus and a method which can freely control the intake air flow rate of an engine for engines utilizing the fuel-first type control.
In the case of air-first control, the output of an engine is changed through a long process that starts with the changing of the opening of the throttle valve followed by a change in the pressure in the intake pipe, a change in the amount of engine intake air, the changing of the fuel flow rate in accordance with the air flow rate and an increase or decrease in the engine output. Since the output of an engine is mainly proportionate to the amount of fuel injection, such control can result in poor engine response because the amount of fuel injection must be changed after the engine intake air flow rate is changed even when the output is to be increased or decreased in a short period. This problem has not been regarded as a significant problem in conventional single point injection (SPI) systems in which fuel is injected upstream of the intake pipe (upstream of the throttle valve) and multi-point injection (MPI) systems in which fuel is injected into a manifold because the time for fuel to reach the combustion chamber of the engine is similar to the time for engine intake air from rate to change, which problem has been difficult to solve.
In the case of a DI engine, however, since it can supply an amount of fuel with better response to a delay of air compared to an SPI or MPI engine, the air-first type control system hinders the improvement of response because of the delay of air in one aspect thereof. While this can be solved by employing the fuel-first type control system, no controller and method have been provided which cause an air flow rate to follow up an amount of fuel injection with high accuracy.
Meanwhile, from the viewpoint of improved safety of automobiles, vehicle movement controlling techniques have been developed such as traction control to prevent slipping of wheels by adjusting engine output, and intelligent cruise control for preventing a collision with a car in front by adjusting engine output. Further, engine output is sometimes controlled in accordance with a gear change for automatic transmission, and engine output control at high speed and with high accuracy is required for such vehicle movement control.
Further, recent environmental regulations permit no increase in harmful components in exhaust gas attributable to fluctuation of an air fuel ratio, which has resulted in a need for reducing fluctuation of an air fuel ratio during acceleration and deceleration. This has resulted in a need for a method and an apparatus for controlling not only fuel but also an engine intake air flow rate.
The output of an engine is directly affected by the amount of fuel which is a source of thermal energy. That is, the output of an engine is determined by the amount of fuel. In the conventional techniques intended for the air-first control, the output of an engine has been indirectly adjusted with air flow rate. Therefore, accurate adjustment of engine output has involved repeated operations of varying the air flow rate first, injecting fuel in accordance therewith, observing the output and appropriately varying the air flow rate again in the case of an excess of shortage, and this has made it difficult to control the output accurately. In the case of a fuel-first control type engine, since the amount of fuel which determines the output is first determined, the engine output can be controlled with high accuracy only by controlling the intake air flow rate of the engine. However, no apparatus and method have been provided which transiently control the intake air flow rate of an engine with high accuracy.
It is an object of the present invention to provide an apparatus and a method for controlling engine intake air and a method for controlling output in which in order to control the output of an engine with high accuracy, when the intake air flow rate of the engine is determined (i.e., the output is determined) in accordance with the amount of fuel, an actual engine intake air flow rate is supplied accurately in accordance therewith.
In order to solve the above problems, there is provided an air flow rate controller which has an air flow rate detecting device for detecting an air flow rate, a throttle valve opening/closing device for opening and closing a throttle valve, and a calculating device to which the detection value of the air flow rate detecting device, the position of the throttle valve, the engine speed and a target engine intake air flow rate are input and in that the calculating device drives the throttle valve opening/closing device in advance such that the engine intake air flow rate agrees with the target engine intake air flow rate.
There is also provided a method for controlling engine intake air flow rate in which a time constant of a delay of response of the air flow rate is calculated and the throttle valve is controlled such that a delay of the engine intake air flow rate is corrected based on the calculated time constant to cause the engine intake air flow rate to follow up the target engine intake air flow rate.
The present invention specifically provides the methods and apparatuses described below.
The present invention provides a method for controlling the flow rate of intake air to an engine by controlling the opening of an electronically controlled throttle, in which a command value for the flow rate of intake air to the engine is calculated from a throttle position signal of the electronically controlled throttle provided in a intake pipe, an air flow rate signal detected by an air flow rate meter provided upstream of the electronically controlled throttle and an engine speed signal and in which a target engine intake air flow rate is calculated by finding an over-shooting amount for said electronically controlled throttle valve.
The present invention further provides a method for controlling the flow rate of intake air to an engine including an over-shooting operation in which a throttle position signal from the electronically controlled throttle, the signal of the air flow rate meter, the engine speed signal and the target engine intake air flow rate to be taken into the cylinders of the engine are input to a calculating device and in which the calculating device determines a time constant of a delay of response, calculates a target signal for an air flow rate meter for compensating for the delay of response based on the determined time constant of the delay of response and drives the electronically controlled throttle such that the signal of the air flow rate meter agrees with the target signal.
The present invention provides a method for controlling the flow rate of intake air to an engine by controlling the opening of an electronically controlled throttle, in which an engine intake air flow rate is obtained from a throttle valve position signal, an air flow rate signal of air flowing through a suction pipe and an engine speed signal; an intake air flow rate command value is calculated in accordance with an amount of fuel injection determined based on said intake air flow rate; a throttle valve position signal is obtained by adding an over-shooting amount to said intake air flow rate command value; and said calculation is repeated by obtaining an engine intake air flow rate from the throttle valve position signal, air flow rate signal and the engine speed signal.
The present invention further provides a method for controlling the flow rate of intake air to an engine in which said over-shooting amount is a compensating (correcting) value determined in advance for the delay of change of the intake air flow rate relative to the operation of the electronically controlled throttle.
The present invention provides a method for controlling the flow rate of intake air to an engine by controlling the opening of an electronically controlled throttle, in which an exhaust gas recirculation flow rate of exhaust gas recirculation for introducing the exhaust gas of the engine into a suction pipe is obtained based on a throttle valve position signal, an air flow rate signal of air flowing through the suction pipe and an engine speed signal; a position signal of an EGR valve is obtained by adding an over-shooting amount to a value corresponding to said exhaust gas recirculation flow rate; and said calculation is repeated by obtaining an exhaust gas recirculation flow rate from said throttle valve position signal, air flow rate signal and engine speed signal.
The present invention provides a method for controlling the flow rate of intake air to an engine having an electronically controlled throttle provided in a suction pipe for introducing air in the internal combustion engine for controlling air flow rate, an air flow rate meter provided upstream of the electronically controlled throttle for detecting the air flow rate, an engine speed meter for detecting engine speed, a calculating device and an EGR valve for an exhaust gas recirculation device for introducing exhaust gas from the internal combustion engine into the suction pipe, in which a throttle position signal from the electronically controlled throttle, an air flow rate meter signal, an engine speed signal, the flow rate of intake air to be taken into the cylinders of the engine and the flow rate of the exhaust gas to be taken into the cylinder of the engine are input to the calculating device; the calculating device determines a time constant for a first delay of response, calculates a target signal for the air flow rate meter to compensate for the delay of response based on the determined time constant for the first delay of response and drives the electronically controlled throttle such that the signal from the air flow rate meter agrees with the target signal; and the calculating device determines a time constant for a second delay of response and drives the EGR valve based on the determined time constant for the second delay of response to compensate for the delay of response of the exhaust gas that flows into the engine.
The present invention provides a device for controlling the flow rate of intake air to an engine having an electronically controlled throttle provided in a suction pipe for introducing air in the engine for controlling air flow rate, an air flow rate meter provided sequence of the electronically controlled throttle valve for detecting the air flow rate and an engine speed meter for detecting engine speed, having a configuration including a calculating device which obtains the flow rate of intake air to the engine from a throttle valve position signal, an air flow rate signal and an engine speed signal, calculates an intake air flow rate command value based on said intake air flow rate, obtains a throttle valve position signal by adding an over-shooting amount to said intake air flow rate command value and repeats said calculation by obtaining an engine intake flow rate from the throttle valve position signal, the air flow rate signal and engine speed signal.
The present invention provides a device for controlling the flow rate of intake air to an engine having an electronically controlled throttle provided in a suction pipe for introducing air in the engine for controlling air flow rate, an air flow rate meter provided upstream of the electronically controlled throttle valve for detecting the air flow rate and an engine speed meter for detecting engine speed, having a configuration including a calculating device which obtains a flow rate of intake air to the engine from a throttle valve position signal, an air flow rate signal and an engine speed signal, obtains an amount of fuel injection from said engine intake air flow rate, calculates an intake air flow rate command value in accordance with said amount of fuel injection, obtains a throttle valve position signal by adding an over-shooting amount to said intake air flow rate command value and repeats said calculation by obtaining an engine intake flow rate from the throttle valve position signal, the air flow rate signal and engine speed signal.
The present invention provides a device for controlling the flow rate of intake air to an engine having an electronically controlled throttle provided in a suction pipe for introducing air in the engine for controlling air flow rate, an air flow rate meter provided upstream of the electronically controlled throttle for detecting the air flow rate, an engine speed meter for detecting engine speed, a calculating device and an EGR valve for an exhaust gas recirculation device for introducing exhaust gas from the engine into the suction pipe, having a configuration including a calculating device to which a throttle position signal from the electronically controlled throttle, an air flow rate meter signal, an engine speed signal, the flow rate of intake air to be taken into the cylinders of the engine and the flow rate of the exhaust gas to be taken into the cylinder of the engine are input, in which the calculating device determines a time constant for a first delay of response, calculates a target signal for the air flow rate meter to compensate for the delay of response based on the determined time constant for the first delay of response and drives the electronically controlled throttle such that the signal from the air flow rate meter agrees with the target signal and in which the calculating device determines a time constant for a second delay of response and drives the EGR valve based on the determined time constant for the second delay of response to compensate for the delay of response of the exhaust gas that flow into the engine.
The present invention provides a method for controlling the output of an engine in which output required for an engine is controlled by a command from an acceleration pedal, in which the torque of an engine is controlled by determining an amount of fuel injection in advance based on an intake air flow rate obtained in a calculating portion, then determining an intake air flow rate command value based on said amount of fuel injection, and determining a target intake air flow rate by adding an over-shooting amount transiently to said intake air flow rate command value to control the opening of an electronically controlled throttle.
According to the invention, once a target engine intake air flow rate is given, a controller predicts the engine intake air flow rate and controls the opening of a throttle valve such to achieve the best approximation of the target engine intake air flow rate. Further, when a target engine intake EGR flow rate is given, an EGR valve is driven such that the EGR valve also achieves the target intake EGR flow rate. As a result, an actual engine intake air flow rate can quickly and accurately reach the target. It is therefore possible to obtain an intake air flow rate which is preferably used in a fuel-first control engine.
This also makes it possible to control the output of an engine taking advantage of the fuel-first type control system.